God's purpose for establishing a covenant with mankind was to have a people who would love Him with their entire being ... spirit, soul, and body.  He wanted a people who were one with Him ... whose wills and desires were in complete harmony and unity with His, whose wills were set to obey Him, submitting their wills to be in line with His will for them.  

Ezekiel 11:19,20 ... God says: "Then I will give them one heart and I will put a new spirit within them.  I will take the stoney heart out of their flesh, and give them a heart of flesh that  they may walk in My statutes and keep My judgments and do them, and they shall be My people and I shall be their God." 

God said that He'd give them (us) one heart and put a new spirit within them (us).  The heart that He's talking about is our soulish heart ... where we live: our mind, our will and our emotions.  Our problem is not with our spirit heart which is in unity with His.  Our problem is with our soulish heart, our soulish being: our will , mind, and emotions.

 Reverend Robert W. & Mary C. Butler